This invention relates generally to a fishing device and, more particularly, to a temperature responsive device that moves to a depth at which the water has a temperature within a range selected by an operator.
It is relatively well known that fish are found in water having a temperature which is to their liking and most conducive to the existence of their species. One reason, besides the temperature itself, is that the oxygen content of the water is dependent on its temperature. It is also known that a thermal differential or gradient usually exists in bodies of water with a relatively warm water temperature being found near the surface and a colder water temperature being found near the bottom.
As a result, persons who know at what water temperature a particular species of fish is likely to be found often measure water temperature at various depths with a thermometer. When the depth at which the desired temperature water is noted, a weight with a lure or hook attached is lowered to that depth. When trolling, a device having a diving plane has been employed which seeks a specific depth when it is pulled through the water. However, the depth at which the device will eventually travel is difficult to determine accurately because that depth is at least partially dependent on its velocity, its weight, the drag or lift generated by its aerodynamic configuration, and the length of line. Further, as the water circulates or as the device is moved through the water, conditions change such that the depth at which a particular water temperature will be found is also likely to change, so that the device no longer lies within the desired temperature range.
Thus it is apparent that it is highly desirable to employ a fishing device or a lure which seeks a depth based solely on a predetermined ambient water temperature. Temperature responsive devices are known in the art, but they are not entirely satisfactory. Illustrative of these devices are Wieszeck U.S. Pat. No. 3,305,964 and Nye U.S. Pat. No. 3,796,000 and U.S. Pat. No. Re. 28,262. Wieszeck shows a variety of devices including a simple bimetal lure having a shape which is altered with varying temperature and a relatively complex device having a vane operated by a thermally responsive bellows. Nye U.S. Pat. No. 3,796,000 and U.S. Pat. No. Re. 28,262 both show a device having a rotatable inclined fin which is controlled by a bimetallic element. The bimetallic element operates a latch which prevents rotation of the fin.
While some of the embodiments illustrated in the foregoing art have means for adjusting the activating temperature of the bimetallic element, none discloses a device in which the upper and lower temperature limits can be adjusted independently. Further, the prior art devices cannot generally be trolled on the surface of the water. It therefore becomes highly desirable to provide a device which overcomes these deficiencies.